Method, medium, and apparatus controlling handover between different networks

ABSTRACT

A method, medium, and apparatus controlling a handover between different network types, including the operations of transmitting a message requesting a transmission bandwidth change, so as to have a transmission bandwidth supported by a new network after movement of the mobile terminal, from the mobile terminal to the server after performing the handover, changing the transmission bandwidth of the server to be supported by the new network based on the transmitted message of requesting the bandwidth change, transmitting a message acknowledging the changed transmission bandwidth from the server to the router, and transceiving data through a new data transmission tunnel between the router and a new access point within the new based on the message acknowledging the changed transmission bandwidth. Accordingly, loss of data packets occuring when a handover is performed may be effectively prevented.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. § 119 from Korean PatentApplication No. 2004-53987, filed on Jul. 12, 2004, the entire contentof which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to methods, media, andapparatuses controlling a handover, and more particularly, to methods,media, and apparatuses controlling a handover, without deteriorating thequality of data transceived when the handover is performed betweendifferent network types.

2. Description of the Related Art

In recent years, the number of wireless Internet users has increased dueto the rapid spread of the Internet, the development of wirelesscommunication technology, and performance enhancements in mobileterminals such as a portable computer and a personal digital assistant(PDA). A mobile terminal may frequently travel from network accesspoints within a wireless Internet environment.

To enable the mobile terminal to perform wireless Internetcommunication, an Internet service having the same high quality as thatof a current network environment should be ensured even when the mobileterminal moves from a current network area to another network area. Inother words, the mobile terminal should perform seamless communication.That is why the handover is derived therefrom, which means a function oftransferring a communication procedure from an access point(hereinafter, it will be referred to as AP) in the current network areato an AP in the next network area. An Inter-Access Point Protocol (IAPP)for communication and handover between APs is defined by the Instituteof Electrical and Electronics Engineers (IEEE).

In the meantime, real time multimedia services, including Video OnDemand (VOD), Audio On Demand (AOD), picture phones, video chatting, andso forth have become popular due to recent Internet developments. Inparticular, such services have become popular due recent wirelessInternet developments and enhancements in processing powers, real timemultimedia services using the mobile terminal have been enabled, andassociated markets are rapidly growing.

By way of the above-mentioned technology developments, it has beenpossible for a user to move while receiving real time multimediaservices through his/her mobile terminal. As a result, this movement isfollowed by a handover of the mobile terminal to the next AP.Accordingly, much research has been conducted on control methods capableof effectively performing the handover.

Conventionally, when the mobile terminal performed the handover, thedifference between a previous transmission Band Width (BW) supported bya previous network, e.g., before movement of the mobile terminal, and atransmission BW supported by a current network terminal was notconsidered. As a result, when the transmission BW supported by theprevious network is larger than that supported by the current network,after movement, loss of data packets was not compensated for due to thedifference of the transmission BWs, which causes the quality of the realtime multimedia service to be deteriorated.

For example, assuming that the previous network, before movement, is aWireless Local Area Network (WLAN), and the current network aftermovement is a 3 Generation Partnership Project (3GPP) wireless network,the WLAN area supports 384 Kbps as the transmission BW, while the 3GPPwireless network area supports 144 Kbps as the transmission BW. When theuser moves from the WLAN area to the 3GPP wireless network area, whilereceiving the real time multimedia, service through his/her own mobileterminal under these environments, there occurs a transmission BWdifference. As a result, the quality of the real time multimedia servicedeteriorates.

SUMMARY OF THE INVENTION

An aspect of the present invention includes solving at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present invention is toprovide a method, medium, and apparatus controlling a handover, which iscapable of transmitting a bandwidth change request message from a mobileterminal to a data providing service by way of an RTCP (RTP ControlProtocol) message packet when the handover is performed betweendifferent kinds of networks.

Another aspect of the present invention is to provide a method, medium,and apparatus controlling a handover, which is capable of transceivingdata through a new second layer tunnel (L2 tunnel; L2-t) by changing acurrent L2-t to a new L2-t by way of an M field of an RTP (Real timeTransport Protocol) packet when the handover is performed betweendifferent kinds of networks.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include a method for controlling a network system,wherein a mobile terminal performs a handover from a first network to asecond network during data transmission and/or reception through anexisting data transmission tunnel between a router and an access pointwithin the first network, including transmitting a message requesting atransmission bandwidth change of the data transmission and/or receptionto a transmission bandwidth supported in the second network, from themobile terminal to a server after performing the handover, changing thetransmission bandwidth of the data transmission and/or reception to thetransmission bandwidth supported by the second network based on thetransmitted message requesting the transmission bandwidth change,transmitting a message acknowledging a changing of the transmissionbandwidth of the data transmission and/or reception, from the server tothe router, after the changing of the transmission bandwidth of the datatransmission and/or reception, and transceiving data through a new datatransmission tunnel between the router and an access point within thesecond network based on the message acknowledging the changing of thetransmission bandwidth of the data transmission and/or reception.

The mobile terminal may perform the handover from the first network tothe second network upon movement of the mobile terminal.

In addition, the transmitting of the message requesting the bandwidthchange may include collecting information, by the mobile terminal,regarding the transmission bandwidth supported by the second networkwhen the handover is performed, determining, by the mobile terminal,whether a difference between a transmission bandwidth supported by thefirst network and the transmission bandwidth supported by the secondnetwork is greater than a predetermined threshold, and transmitting themessage requesting the bandwidth change from the mobile terminal to theserver upon the determination that the difference is greater than thepredetermined threshold.

Further, the method may include transmitting a vertical handover (VHO)request message from the mobile terminal to the router upon the handoverbeing performed, and building, by the router, the new data transmissiontunnel based on the transmitted VHO request message, as well as enteringa standby mode, by the router, maintaining the data transmission and/orreception through the existing data transmission tunnel based on thetransmitted VHO request message, and wherein the transceiving of thedata transmission and/or reception includes having the router change thedata transmission and/or reception from the existing data transmissiontunnel to the new data transmission tunnel when the messageacknowledging the changing of the transmission bandwidth of the datatransmission and/or reception is transmitted.

The message requesting the bandwidth change may use an application (APP)message among RTP control protocol (RTCP) messages. In addition, themessage acknowledging the changing of the transmission bandwidth of thedata transmission and/or reception may use a real time transportprotocol (RTP) in which an M field is set to 1.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include a method for controlling a mobile terminalin a network system, wherein the mobile terminal performs a handoverfrom a first network to a second network during data transmission and/orreception through an existing data transmission tunnel between a routerand an access point within the first network, including transmitting toa server a message requesting a bandwidth change of the datatransmission and/or reception to a transmission bandwidth supported bythe second network after performing the handover, and transceiving datathrough a new data transmission tunnel between the router and an accesspoint within the second network when a message acknowledging a changingof the transmission bandwidth of the data transmission and/or reception,based on the transmitted message requesting the bandwidth change, istransmitted from the server to the router.

The transmitting of the message requesting the bandwidth change mayinclude collecting information with respect to the transmissionbandwidth supported by the second network when the handover isperformed, determining whether a difference between the transmissionbandwidth supported by the second network and a transmission bandwidthsupported by the first network is greater than a predeterminedthreshold, and transmitting the message requesting the bandwidth changeto the server upon the determination whether the difference is greaterthan the predetermined threshold.

The method may further include transmitting a vertical handover (VHO)request message to the router when the handover is performed, andtransceiving data with the router, which has entered a standby mode ofmaintaining the data transmission and/or reception through the existingdata transmission tunnel, based on the transmitted VHO request message.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include a method for controlling a router in anetwork system, wherein a mobile terminal performs a handover from afirst network to a second network during data transmission and/orreception through an existing data transmission tunnel between a routerand an access point within the first network, including receiving avertical handover (VHO) request message from the mobile terminal,building a new data transmission tunnel between the router and an accesspoint within the second network based on the received VHO requestmessage, and transceiving data through the new data transmission tunnelbetween the router and the access point within the second network when amessage acknowledging a changing of the transmission bandwidth of thedata transmission and/or reception, based on a message from the mobileterminal to the server requesting a transmission bandwidth change of thedata transmission and/or reception so as to have a transmissionbandwidth supported by the second network, is received from the server.

The transceiving of the data may include receiving from the server themessage acknowledging the changing of the transmission bandwidth of thedata transmission and/or reception, changing the data transmissionand/or reception from the existing data transmission tunnel to the newdata transmission tunnel based on the received message acknowledging thechanging of the transmission bandwidth of the data transmission and/orreception, and transceiving data through the new data transmissiontunnel.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include at least one medium including computerreadable code implementing embodiments of the present invention.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include a network system, wherein a mobileterminal performs a handover from a first network to a second networkduring data transmission and/or reception through an existing datatransmission tunnel between a router and an access point within thefirst network, including the mobile terminal to transmit to a server amessage requesting a transmission bandwidth change of the datatransmission and/or reception to a transmission bandwidth supported inthe second network, after performing the handover, the server to changethe transmission bandwidth of the data transmission and/or reception tothe transmission bandwidth supported by the second network based onreceipt of the message requesting the transmission bandwidth change, andto transmit a message to the router acknowledging a changing of thetransmission bandwidth of the data transmission and/or reception, afterthe changing of the transmission bandwidth of the data transmissionand/or reception, and the router to transceive data through a new datatransmission tunnel between the router and an access point within thesecond network based on the message acknowledging the changing of thetransmission bandwidth of the data transmission and/or reception.

The mobile terminal may perform the handover from the first network tothe second network upon movement of the mobile terminal.

In the transmitting of the message requesting the bandwidth change, themobile terminal may collect information regarding the transmissionbandwidth supported by the second network when the handover isperformed, determine whether a difference between a transmissionbandwidth supported by the first network and the transmission bandwidthsupported by the second network is greater than a predeterminedthreshold, and transmit the message requesting the bandwidth change tothe server upon the determination that the difference is greater thanthe predetermined threshold.

The mobile terminal may also transmit a vertical handover (VHO) requestmessage to the router upon the handover being performed and the routerbuilds the new data transmission tunnel based on the transmitted VHOrequest message.

The router may enter a standby mode to maintain the data transmissionand/or reception through the existing data transmission tunnel based onthe transmitted VHO request message, and the router may change the datatransmission and/or reception from the existing data transmission tunnelto the new data transmission tunnel when the message acknowledging thechanging of the transmission bandwidth of the data transmission and/orreception is received.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include a mobile terminal to at least perform ahandover from a first network to a second network during datatransmission and/or reception through an existing data transmissiontunnel between a router and an access point within the first network,transmit to a server a message requesting a bandwidth change of the datatransmission and/or reception to a transmission bandwidth supported bythe second network after performing the handover, and transceive datathrough a new data transmission tunnel between the router and an accesspoint within the second network when a message acknowledging a changingof the transmission bandwidth of the data transmission and/or reception,based on the transmitted message requesting the bandwidth change, istransmitted from the server to the router.

In the transmitting of the message requesting the bandwidth change, themobile terminal may collect information with respect to the transmissionbandwidth supported by the second network when the handover isperformed, determine whether a difference between the transmissionbandwidth supported by the second network and a transmission bandwidthsupported by the first network is greater than a predeterminedthreshold, and transmit the message requesting the bandwidth change tothe server upon the determination whether the difference is greater thanthe predetermined threshold.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention include a router, in a network system wherein amobile terminal performs a handover from a first network to a secondnetwork during data transmission and/or reception through an existingdata transmission tunnel between the router and an access point withinthe first network, to at least receive a vertical handover (VHO) requestmessage from the mobile terminal, build a new data transmission tunnelbetween the router and an access point within the second network basedon the received VHO request message, and transceive data through the newdata transmission tunnel between the router and the access point withinthe second network when a message acknowledging a changing of thetransmission bandwidth of the data transmission and/or reception, basedon a message from the mobile terminal to the server requesting atransmission bandwidth change of the data transmission and/or receptionso as to have a transmission bandwidth supported by the second network,is received from the server.

In the transceiving of the data, the router may at least receive fromthe server the message acknowledging the changing of the transmissionbandwidth of the data transmission and/or reception, change the datatransmission and/or reception from the existing data transmission tunnelto the new data transmission tunnel based on the received messageacknowledging the changing of the transmission bandwidth of the datatransmission and/or reception, and transceive data through the new datatransmission tunnel.

In addition, the router may enter a standby mode of maintaining datatransmission and/or reception through the new data transmission tunnelbased on the received VHO request message, and change the datatransmission and/or reception from the existing data transmission tunnelto the new data transmission tunnel when the message acknowledging thechanging of the transmission bandwidth of the data transmission and/orreception is received during the standby mode.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be apparentfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 illustrates a handover between different network types, accordingto an embodiment of the present invention;

FIG. 2 illustrates a handover control procedure applied when a handoveris performed between different network types, according to an embodimentof the present invention;

FIG. 3 illustrates a flow chart for a handover control procedure basedon a mobile terminal, according to an embodiment of the presentinvention;

FIG. 4 illustrates a flow chart for a handover control procedure basedon real-time transport protocol (RTP)/RTP control protocol (RTCP)processing, according to an embodiment of the present invention; and

FIG. 5 illustrates a flow chart for a handover control procedure basedon a crossover router, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

FIG. 1 illustrates a procedure for performing a handover betweendifferent network types, in accordance with an embodiment of the presentinvention.

Referring to FIG. 1, wireless networks 1000 and 2000 include respectiveAPs 110 and 120 and a mobile terminal 100, such as a portable computeror a PDA, which performs wireless communication with the APs 110 and120. The APs 110 and 120 may connect a wired LAN with a wireless LAN soas to allow a user using the mobile terminal 100 to readily connect tothe Internet, for example.

Referring back to FIG. 1, the mobile terminal 100 can perform a handoverfrom the first AP 110 within the first network 1000, which will beconsidered the previous network, to a second AP 120 within the secondnetwork 2000, which will be considered the current network, i.e., aftermovement of the mobile terminal. In this case, a dual mode terminalwhich is capable of simultaneously accessing two wireless channels maybe employed for the mobile terminal 100.

Whether the mobile terminal 100 has performed the handover may bedetermined by having the mobile terminal 100 analyze a channel state ofa received signal. In this case, the intensity or the electric energy ofthe received signal may be used for analyzing the channel state. Themobile terminal 100 can compare the intensity or the electric energy ofthe received signal with a predetermined threshold value, and determinethat the handover was performed when the intensity or the electricenergy of the received signal is not more than the predeterminedthreshold value. However, the present invention is not limited to theabove-mentioned method for determining whether the handover has beenperformed.

The mobile terminal 100 can perform the handover from the first network1000 to the second network 2000, again noting that the first and secondnetworks 1000 and 2000 may support different transmission BWs when theyare different types of networks, e.g., one network being a WLAN and theother being a 3GPP network.

According to an embodiment of the present invention, the mobile terminal100 can transmit to a data providing server a message requesting thedata providing server to change a transmission BW to one supported bythe second network 2000, and the data providing server in turn canchange the transmission BW to transmit data packets within thetransmission BW supported by the second network 2000.

FIG. 2 illustrates a diagram for a handover control procedure appliedwhen the handover is performed between different network types, inaccordance with and embodiment of the present invention.

Referring to FIGS. 1 and 2, the mobile terminal 100 wirelesslyconneected to the first AP 110 can receive data from the data providingserver 140 through a crossover router 130, for example. In this case,the crossover router 130 transceives data with the firstAP 110, throughan existing second layer tunnel, for example. The second layer tunnelmeans another connection generated between the first AP 110 and thecrossover router 130 based on the wireless resource provided from thefirst network 1000 including the first AP 110.

When the mobile terminal 100 moves from the first network 1000 area tothe second network 2000 area, that is, when the mobile terminal 100performs the handover, the mobile terminal 100 transmits a verticalhandover request message (VHO-request message) to the crossover router130. The crossover router 130 can then build a new second layer tunnelbased on the received VHO-request message. In this case, the new secondlayer tunnel means another connection generated between the second AP120 and the crossover router 130 based on the wireless resource providedfrom the second network 2000 including the second AP 120.

The crossover router 130, which has built the new second layer tunnelfor the second AP 120, can enter a standby mode. In this case, thestandby mode means a mode in which the crossover router 130 uses theexisting second layer tunnel for transceiving data even though thecrossover router 130 has built the new second layer tunnel. Previously,the new second layer tunnel may have been built but was immediatelyemployed to transceive data. As such, the transmission BW difference wasnot taken into consideration, which can cause some data packets to belost due to the transmission BW difference.

In addition, when the mobile terminal 100 performs the handover, themobile terminal 100 can transmit a message of requesting a BW change tothe data providing server 140. In this case, prior to transmission ofthe message, the mobile terminal 100 can collect information withrespect to the second network 2000, after it performs the handover, andwill determine whether a BW difference even exists.

In the meantime, an Application (APP) message among RTCP messages may beapplied, as the message of requesting the BW change. The RTCP messagesgenerally include a Sender Report (SR) message, a Receiver Report (RR)message, a Source DEScription (SDES) message, a BYE (BYE) message, anAPPlication (APP) message, and so forth, with the APP message being usedfor designating a new function limited to a new application when the newapplication or the new function is tested.

In addition, the RTCP messages are typically and periodically providedfrom the mobile terminal 100 to the data providing server 140. However,when the APP message is employed for the message requesting the BWchange, as in embodiments of the present invention, the mobile terminal100 not only periodically transmits the RTCP message to the dataproviding server 140 but processes the RTCP message to be transmitted tothe data providing server 140 even when it has performed the handover.Hereinafter, as an example, the APP message will be employed as themessage requesting the BW difference among the RTCP messages, however,it is apparent that the present invention is not limited thereto.

In the meantime, the data providing server 140 can change the appliedtransmission BW for the mobile terminal 100 based on the receivedmessage of requesting the BW change. Methods for changing thetransmission BW may include a method for changing an encoding rate, anda method for not transmitting one flow in a session including aplurality of the flows, however, embodiments of the present inventionare not necessarily limited to these above-mentioned case.

After the data providing server 140 changes the transmission BW, thedata providing server 140 can transmit a message acknowledging the BWchange to the crossover router 130. An RTP packet can be applied for themessage acknowledging the BW change.

The RTP packet typically includes a V field as a version field, a Pfield used to form a packet on a 32 bit basis, an X field as anextension field, a CC field indicating the number of Contributing Source(CRSC) identifiers in a fixed header, an M field indicating a frame areawith respect to multimedia information and used for discriminatingvoice, picture information, and so forth within a packet, a PT fieldindicating a RTP payload format of a profile defined by the Request forComments (RFC) 1890, a sequence number field used for detecting a packetloss and storing again a packet order, etc. According to an embodimentof the present invention, when the RTP packet is applied as the messageof acknowledging the BW change, after the data providing server 140changes the transmission BW, the M field of the RTP packet is set to 1.

Hereinafter, only as an example, the RTP message will be applied as themessage of acknowledging the BW change, however, it is apparent that thepresent invention is not limited thereto.

The crossover router 130 can then transceive various data with themobile terminal 100 through the new second layer tunnel instead of theexisting second layer tunnel based on the received message ofacknowledging the BW change.

Accordingly, even after the mobile terminal 100 performs the handover,it may still receive seamless real time multimedia services.

FIG. 3 illustrates a flow chart for a handover control procedure basedon a mobile terminal, in accordance with and embodiment of the presentinvention.

Referring to FIGS. 1 to 3, the mobile terminal 100 can be wirelesslyconnected to the first AP 110 and transceive various data and messageswith the first AP 110, through the existing second layer tunnel(operation S200). When the mobile terminal 100 moves out of the firstnetwork 1000 area into the second network 2000 area to perform thehandover, so that it is triggered from the second layer (L2: data linklayer) to the third layer (L3: application layer) (operation S210), themobile terminal 100 collects information with respect to the secondnetwork 2000, i.e., the new network, in particular, collects informationwith respect to supported transmission BWs (operation S220). The mobileterminal 100 then compares the transmission BW capabilities (e.g., BWsizes) supported by the first network 1000 with that supported by thesecond network 2000 (operation S230). When the BW difference is greaterthan a predetermined threshold, such that the transmission BW needs tobe changed, the mobile terminal 100 recognizes the fact that thetransmission BW needs to be changed (operation S240). The mobileterminal 100 then transmits the VHO-request message to the crossoverrouter 130 (operation S250) and the message requesting the BW change tothe data providing server 140, as described above (operation S260).After the predetermined procedures are performed between the crossoverrouter 130 and the data providing server 140, the mobile terminal 100 iswirelessly connected to the second AP 120 and transceives the variousdata and messages through the new second layer tunnel (operation S270).

FIG. 4 illustrates a flow chart for a handover control procedure basedon RTP/RTCP processing, in accordance with an embodiment of the presentinvention.

Referring to FIGS. 1, 2 and 4, the mobile terminal 100 can set apredetermined time, by way of an internal timer (not shown) (operationS300). In this case, the predetermined time means a set point of timefor periodically transmitting the RTCP message packet to the dataproviding server 140. When the predetermined time is set (operationS300) and the set predetermined time has terminated (operation S310),the RTCP message packet is transmitted from the mobile terminal 100 tothe data providing server 140 (operation S340). In this case, the RTCPmessage to be transmitted is a typical RTCP message containinginformation with respect to the transmitted multimedia data packet lossand so forth.

In addition, when the handover is performed and the difference of thetransmission BWs is greater than the predetermined threshold, evenbefore the set predetermined time has terminated (operation S320), theRTCP message packet is transmitted from the mobile terminal 100 to thedata providing server 140 (operation S340). However, the RTCP message tobe transmitted in this case is not the typical message but the messageof requesting the transmission BW change, as described above.

In the meantime, when the predetermined time has not terminated and thehandover has not been performed, a typical RTC packet is transmitted(operation S330).

FIG. 5 illustrates a flow chart explaining a handover control procedurebased on a crossover router, in accordance with an embodiment of thepresent invention.

Referring to FIGS. 1, 2 and 5, the crossover router 130 can be linked tothe first AP 110, through the existing second layer tunnel, andtransceives various data and messages with the mobile terminal 100(operation S400). The crossover router 130 builds a new second layertunnel for the second AP 120 (operation S420) when it receives theVHO-request message (operation S410).

In addition, the crossover router 130 enters the VHO standby mode(operation S430). The crossover router 130 can then check the M field ofthe RTP packet to determine whether it is set to 1, for example, when itreceives the RTP packet from the data providing server 140. In otherwords, the crossover router 130 determines whether the RTP packet is amessage of acknowledging the transmission BW change (operation S450).Upon determination that the RTP packet is the message acknowledging thetransmission BW change, the crossover router 130 changes the datatransmission tunnel from the existing second layer tunnel to the newsecond layer tunnel (operation S460), and transceives various data andvarious messages with the mobile terminal 100 through the new secondlayer tunnel (operation S470).

In addition to the above described embodiments, embodiments of thepresent invention can also be implemented through computer readablecode/instructions in/on a medium, e.g., a computer readable medium. Themedium can correspond to any medium/media permitting the storing and/ortransmission of the computer readable code.

The computer readable code can be recorded/transferred on/in a medium ina variety of ways, with examples of the medium including magneticstorage media (e.g., ROM, floppy disks, hard disks, etc.), opticalrecording media (e.g., CD-ROMs, or DVDs), and storage/transmission mediasuch as carrier waves, as well as through the Internet, for example. Themedium may also be a distributed network, so that the computer readablecode is stored/transferred and implemented in a distributed fashion.

In accordance with the above method controlling the handover, thetransmission BW difference between different kinds of networks may betaken into consideration to perform the handover when the real timemultimedia service is provided at a fast speed through a wirelessInternet, for example, so that the data packet loss may be effectivelyremoved. In addition, the present invention has an advantage that it maybe applied to any differing types of networks having differingtransmission BWs.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A method for controlling a network system, wherein a mobile terminalperforms a handover from a first network to a second network during datatransmission and/or reception through an existing data transmissiontunnel between a router and an access point within the first network,comprising: transmitting a message requesting a transmission bandwidthchange of the data transmission and/or reception to a transmissionbandwidth supported in the second network, from the mobile terminal to aserver after performing the handover; changing the transmissionbandwidth of the data transmission and/or reception to the transmissionbandwidth supported by the second network based on the transmittedmessage requesting the transmission bandwidth change; transmitting amessage acknowledging a changing of the transmission bandwidth of thedata transmission and/or reception, from the server to the router, afterthe changing of the transmission bandwidth of the data transmissionand/or reception; and transceiving data through a new data transmissiontunnel between the router and an access point within the second networkbased on the message acknowledging the changing of the transmissionbandwidth of the data transmission and/or reception.
 2. The method ofclaim 1, wherein the mobile terminal performs the handover from thefirst network to the second network upon movement of the mobileterminal.
 3. The method of claim 1, wherein the transmitting of themessage requesting the bandwidth change comprises: collectinginformation, by the mobile terminal, regarding the transmissionbandwidth supported by the second network when the handover isperformed; determining, by the mobile terminal, whether a differencebetween a transmission bandwidth supported by the first network and thetransmission bandwidth supported by the second network is greater than apredetermined threshold; and transmitting the message requesting thebandwidth change from the mobile terminal to the server upon thedetermination that the difference is greater than the predeterminedthreshold.
 4. The method of claim 1, further comprising: transmitting avertical handover (VHO) request message from the mobile terminal to therouter upon the handover being performed; and building, by the router,the new data transmission tunnel based on the transmitted VHO requestmessage.
 5. The method of claim 4, further comprising: entering astandby mode, by the router, maintaining the data transmission and/orreception through the existing data transmission tunnel based on thetransmitted VHO request message, and wherein the transceiving of thedata transmission and/or reception includes having the router change thedata transmission and/or reception from the existing data transmissiontunnel to the new data transmission tunnel when the messageacknowledging the changing of the transmission bandwidth of the datatransmission and/or reception is transmitted.
 6. The method of claim 1,wherein the message requesting the bandwidth change uses an application(APP) message among RTP control protocol (RTCP) messages.
 7. The methodof claim 1, wherein the message acknowledging the changing of thetransmission bandwidth of the data transmission and/or reception uses areal time transport protocol (RTP) in which an M field is set to
 1. 8. Amethod for controlling a mobile terminal in a network system, whereinthe mobile terminal performs a handover from a first network to a secondnetwork during data transmission and/or reception through an existingdata transmission tunnel between a router and an access point within thefirst network, comprising: transmitting to a server a message requestinga bandwidth change of the data transmission and/or reception to atransmission bandwidth supported by the second network after performingthe handover; and transceiving data through a new data transmissiontunnel between the router and an access point within the second networkwhen a message acknowledging a changing of the transmission bandwidth ofthe data transmission and/or reception, based on the transmitted messagerequesting the bandwidth change, is transmitted from the server to therouter.
 9. The method of claim 8, wherein the mobile terminal performsthe handover from the first network to the second network upon movementof the mobile terminal.
 10. The method of claim 8, wherein thetransmitting of the message requesting the bandwidth change comprises:collecting information with respect to the transmission bandwidthsupported by the second network when the handover is performed;determining whether a difference between the transmission bandwidthsupported by the second network and a transmission bandwidth supportedby the first network is greater than a predetermined threshold; andtransmitting the message requesting the bandwidth change to the serverupon the determination whether the difference is greater than thepredetermined threshold.
 11. The method of claim 8, further comprising:transmitting a vertical handover (VHO) request message to the routerwhen the handover is performed; and transceiving data with the router,which has entered a standby mode of maintaining the data transmissionand/or reception through the existing data transmission tunnel, based onthe transmitted VHO request message.
 12. The method of claim 8, whereinthe message requesting the bandwidth change uses an application (APP)message among RTP control protocol (RTCP) messages.
 13. The method ofclaim 8, wherein the message acknowledging the changing of thetransmission bandwidth uses a real time transport protocol (RTP) inwhich an M field is set to
 1. 14. A method for controlling a router in anetwork system, wherein a mobile terminal performs a handover from afirst network to a second network during data transmission and/orreception through an existing data transmission tunnel between a routerand an access point within the first network, comprising: receiving avertical handover (VHO) request message from the mobile terminal;building a new data transmission tunnel between the router and an accesspoint within the second network based on the received VHO requestmessage; and transceiving data through the new data transmission tunnelbetween the router and the access point within the second network when amessage acknowledging a changing of the transmission bandwidth of thedata transmission and/or reception, based on a message from the mobileterminal to the server requesting a transmission bandwidth change of thedata transmission and/or reception so as to have a transmissionbandwidth supported by the second network, is received from the server.15. The method of claim 14, wherein the mobile terminal performs thehandover from the first network to the second network upon movement ofthe mobile terminal.
 16. The method of claim 14, wherein thetransceiving of the data comprises: receiving from the server themessage acknowledging the changing of the transmission bandwidth of thedata transmission and/or reception; changing the data transmissionand/or reception from the existing data transmission tunnel to the newdata transmission tunnel based on the received message acknowledging thechanging of the transmission bandwidth of the data transmission and/orreception; and transceiving data through the new data transmissiontunnel.
 17. The method of claim 16, further comprising: entering astandby mode of maintaining data transmission and/or reception throughthe new data transmission tunnel based on the received VHO requestmessage, and wherein the changing of the data transmission tunnelincludes changing from the existing data transmission tunnel to the newdata transmission tunnel when the message acknowledging the changing ofthe transmission bandwidth of the data transmission and/or reception isreceived during the standby mode.
 18. The method of claim 14, whereinthe message acknowledging the changing of the transmission bandwidth ofthe data transmission and/or reception uses a real time transportprotocol (RTP) in which an M field is set to
 1. 19. The method of claim14, wherein the message requesting the bandwidth change uses anapplication (APP) message among RTP control protocol (RTCP) messages.20. At least one medium comprising computer readable code implementingthe method of claim
 1. 21. At least one medium comprising computerreadable code implementing the method of claim
 8. 22. At least onemedium comprising computer readable code implementing the method ofclaim
 14. 23. A network system, wherein a mobile terminal performs ahandover from a first network to a second network during datatransmission and/or reception through an existing data transmissiontunnel between a router and an access point within the first network,comprising: the mobile terminal to transmit to a server a messagerequesting a transmission bandwidth change of the data transmissionand/or reception to a transmission bandwidth supported in the secondnetwork, after performing the handover; the server to change thetransmission bandwidth of the data transmission and/or reception to thetransmission bandwidth supported by the second network based on receiptof the message requesting the transmission bandwidth change, and totransmit a message to the router acknowledging a changing of thetransmission bandwidth of the data transmission and/or reception, afterthe changing of the transmission bandwidth of the data transmissionand/or reception; and the router to transceive data through a new datatransmission tunnel between the router and an access point within thesecond network based on the message acknowledging the changing of thetransmission bandwidth of the data transmission and/or reception. 24.The system of claim 23, wherein the mobile terminal performs thehandover from the first network to the second network upon movement ofthe mobile terminal.
 25. The system of claim 23, wherein, in thetransmitting of the message requesting the bandwidth change, the mobileterminal collects information regarding the transmission bandwidthsupported by the second network when the handover is performed,determines whether a difference between a transmission bandwidthsupported by the first network and the transmission bandwidth supportedby the second network is greater than a predetermined threshold, andtransmits the message requesting the bandwidth change to the server uponthe determination that the difference is greater than the predeterminedthreshold.
 26. The system of claim 23, wherein the mobile terminaltransmits a vertical handover (VHO) request message to the router uponthe handover being performed and the router builds the new datatransmission tunnel based on the transmitted VHO request message. 27.The system of claim 26, wherein the router enters a standby mode tomaintain the data transmission and/or reception through the existingdata transmission tunnel based on the transmitted VHO request message,and the router changes the data transmission and/or reception from theexisting data transmission tunnel to the new data transmission tunnelwhen the message acknowledging the changing of the transmissionbandwidth of the data transmission and/or reception is received.
 28. Thesystem of claim 23, wherein the message requesting the bandwidth changeuses an application (APP) message among RTP control protocol (RTCP)messages.
 29. The system of claim 23, wherein the message acknowledgingthe changing of the transmission bandwidth of the data transmissionand/or reception uses a real time transport protocol (RTP) in which an Mfield is set to
 1. 30. A mobile terminal to at least perform a handoverfrom a first network to a second network during data transmission and/orreception through an existing data transmission tunnel between a routerand an access point within the first network, transmit to a server amessage requesting a bandwidth change of the data transmission and/orreception to a transmission bandwidth supported by the second networkafter performing the handover, and transceive data through a new datatransmission tunnel between the router and an access point within thesecond network when a message acknowledging a changing of thetransmission bandwidth of the data transmission and/or reception, basedon the transmitted message requesting the bandwidth change, istransmitted from the server to the router.
 31. The mobile terminal ofclaim 30, wherein the mobile terminal performs the handover from thefirst network to the second network upon movement of the mobileterminal.
 32. The mobile terminal of claim 30, wherein, in thetransmitting of the message requesting the bandwidth change, the mobileterminal collects information with respect to the transmission bandwidthsupported by the second network when the handover is performed,determines whether a difference between the transmission bandwidthsupported by the second network and a transmission bandwidth supportedby the first network is greater than a predetermined threshold, andtransmits the message requesting the bandwidth change to the server uponthe determination whether the difference is greater than thepredetermined threshold.
 33. The mobile terminal of claim 30, whereinthe mobile terminal transmits a vertical handover (VHO) request messageto the router when the handover is performed, and transceives data withthe router, which has entered a standby mode of maintaining the datatransmission and/or reception through the existing data transmissiontunnel, based on the transmitted VHO request message.
 34. The mobileterminal of claim 30, wherein the message requesting the bandwidthchange uses an application (APP) message among RTP control protocol(RTCP) messages.
 35. The mobile terminal of claim 30, wherein themessage acknowledging the changing of the transmission bandwidth uses areal time transport protocol (RTP) in which an M field is set to
 1. 36.A router, in a network system wherein a mobile terminal performs ahandover from a first network to a second network during datatransmission and/or reception through an existing data transmissiontunnel between the router and an access point within the first network,to at least receive a vertical handover (VHO) request message from themobile terminal, build a new data transmission tunnel between the routerand an access point within the second network based on the received VHOrequest message, and transceive data through the new data transmissiontunnel between the router and the access point within the second networkwhen a message acknowledging a changing of the transmission bandwidth ofthe data transmission and/or reception, based on a message from themobile terminal to the server requesting a transmission bandwidth changeof the data transmission and/or reception so as to have a transmissionbandwidth supported by the second network, is received from the server.37. The router of claim 36, wherein the mobile terminal performs thehandover from the first network to the second network upon movement ofthe mobile terminal.
 38. The router of claim 36, wherein, in thetransceiving of the data, the router at least receives from the serverthe message acknowledging the changing of the transmission bandwidth ofthe data transmission and/or reception, changes the data transmissionand/or reception from the existing data transmission tunnel to the newdata transmission tunnel based on the received message acknowledging thechanging of the transmission bandwidth of the data transmission and/orreception, and transceives data through the new data transmissiontunnel.
 39. The router of claim 38, wherein the router enters a standbymode of maintaining data transmission and/or reception through the newdata transmission tunnel based on the received VHO request message, andchanges the data transmission and/or reception from the existing datatransmission tunnel to the new data transmission tunnel when the messageacknowledging the changing of the transmission bandwidth of the datatransmission and/or reception is received during the standby mode. 40.The router of claim 36, wherein the message acknowledging the changingof the transmission bandwidth of the data transmission and/or receptionuses a real time transport protocol (RTP) in which an M field is setto
 1. 41. The router of claim 36, wherein the message requesting thebandwidth change uses an application (APP) message among RTP controlprotocol (RTCP) messages.